To reduce CO2-emissions lightweight structures needs to be implemented in all transport applications. At the same time, low-weight and high performance materials must provide safety and reliability, at economical prices. Extended Non-Destructive Testing (ENDT) contributes to safeguarding the performance of adhesively joined load-critical structures, permitting to steadily monitor adherent surfaces prior to bonding and to detect adhesion properties of bonded components. In the present work, approaches exceeding the state-of-the-art of innovative ENDT techniques like robot-based Laser-Induced Breakdown Spectroscopy (LIBS) are presented. Furthermore, automated, AI-based image processing and evaluation methods for surface quality inspection are shown, aiming at overcoming today’s limitations concerning handling, evaluation speed and reliability of results. First results of automated in-line surface quality assurance approaches for assessing multi material adherent surfaces are highlighted.
Composite materials are commonly used in many branches of industry. One of the effective methods to join CFRP parts is to use adhesives. There is a search of effective methods for quality assurance of bonded parts. There is a need for pre- and post-bond inspection to ensure proper bonding and verify its quality. Research reported here focuses on post-bond inspection of bonded CFRP parts. In this paper we report investigations of samples that were modified in order to simulate the conditions that can be encountered during the bonding repair processes. The modifications were made before adhesive bonding, and their effect on the quality of the bond is studied. The first case was the thermal treatment. It was made by exposure of samples to elevated temperatures. This case accounts for parts that may be exposed to external heat source or lightening impact. Second of the investigated cases was deicing fluid contamination prepared by dip-coating of clean CFRP plates. When cleaning the aircraft for a repair this fluid can be transported to bonding areas and weaken the joint. The third type of modification was faulty curing of the adhesive. It was prepared by local pre-curing of the adhesive. Pre-curing causes irregularities in the curing of the adhesive joint. Apart from single modifications, also mixed cases were studied, as well as scarf bonding. The samples were studied in non-destructive approach. It was shown that for some of the cases the detection is possible.
Composite materials are commonly used in many branches of industry. One of the effective methods to join CFRP parts is the adhesive bonding. There is a search of effective methods for quality assurance of bonded parts. There is a need for pre- and post-bond inspection to ensure proper bonding and verify its quality. Research reported here focuses on post-bond inspection of bonded CFRP parts. In this paper we report investigations of samples that were modified with contamination that can be encountered during the manufacturing process of the CFRP parts. The contaminations were introduced before adhesive bonding, and the effect of the contamination on the quality bond is studied. First of the investigated cases was release agent contamination prepared by dip-coating of clean CFRP plates. The release agent is used during the production of composite elements and can contaminate the surface to be bonded. The second case was the moisture contamination. It was obtained by conditioning of the samples in humid conditions. Moisture contamination can be gained from water-coupled ultrasonics or during transportation of unprotected parts. The third type of contamination had more local character. It simulated fingerprints. Artificial sweat was used. The fingerprint contamination can be caused by improper handling of the parts. Apart from single contamination, also mixed contamination cases were studied, as well as curved samples. The samples were studied in non-destructive approach. It was shown that for some of the cases the detection is possible.
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